# Controlled Polymerization Catalysis for the Synthesis of Degradable Amphiphilic Polycarbonates from CO2

## TL;DR

Scientists created a new type of water-soluble, degradable polymer from CO2 and glycerol, which can self-assemble into nanostructures and break down in alkaline conditions.

## Contribution

A novel heterodinuclear catalyst enables controlled synthesis of CO2-based degradable polycarbonates with tunable properties.

## Key findings

- The [Co(III)/K(I)] catalyst allows controlled ring-opening copolymerization of CO2 and epoxide with low dispersity and predictable molecular weights.
- The resulting polycarbonates self-assemble into nanostructures in water and degrade in alkaline solutions via self-immolative backbiting.
- Degradation occurs within minutes to a month, depending on pH and end-group chemistry, producing nontoxic small molecules.

## Abstract

Synthetic water-soluble polymers are ubiquitous in solution-based
applications, but their petroleum origin and nondegradable bonds create
environmental concerns. Here, CO2- and glycerol-derived
polycarbonates incorporating hydrophilic diglycerol motifs are prepared
as a general-purpose water-soluble degradable polymer platform. A
high-performance heterodinuclear [Co­(III)/K­(I)] catalyst enables controlled
ring-opening copolymerization (ROCOP) of CO2 with an acetal-protected
epoxide, delivering well-defined polycarbonates with low dispersity
(D̵ < 1.2) and predictable molecular weights
(≈2000–20,000 g mol–1). The catalysis
is tolerant to protic initiators (chain transfer agents, CTAs), enabling
control over both chain length and end-group chemistry. Deprotection
of the acetals is quantitative and affords water-soluble polycarbonates
incorporating hydrophilic diglycerol motifs. Using natural hydrophobic
initiators yields amphiphilic polymers that self-assemble in water
to form nanostructures of ≈7–11 nm with a critical micelle
concentration of ≈30 mg L–1. These polymers
are stable at either neutral or acidic pH but depolymerize in alkaline
solution to form nontoxic small molecules. Degradation proceeds by
hydroxyl chain-end–initiated backbiting, i.e. by self-immolation,
with pH- and end-cap-dependent kinetics, with complete degradation
occurring over minutes to one month. Overall, this renewable polycarbonate
chemistry, which is ∼23 wt % CO2-derived; ∼77
wt % glycerol-derived, combines precise polymerization catalysis,
spontaneous aqueous self-assembly and controllable aqueous degradability
which are important for next-generation surfactants.